The bottom of the lower triple clamp needed to be milled to provide clearance. This would mean a trip to the machine shop. Neil from Arizona mentioned a milling cutter in an earlier post on this build diary. This made me think about milling the part on my drill press. It would be bush engineering, but it would save time and money.

The local Fastenal shop ordered me a 4 tooth by 1/2 inch diameter end mill cutter. I made sure the cutter would make plunge cuts. Not all end mill cutters will plunge. The 1/2 inch size is the biggest I use on a drill press based on experience. The stronger vertical milling machines are needed for the bigger cutters.

I taped a piece of graph paper with a 1/4 inch square grid on the drill press table. Then I clamped on a guide bar with two clamps. The bar was lined up with the grid on the paper. Next, I clamped the part onto the table with two husky C clamps. The part rested against the guide bar and a pen mark on the part was aligned with a line on the grid paper. The stop was set so the cutter would not go deeper than the desired 1/4 inch.

I slid the part along the guide and plunged the mill cutter into the part at 1/4 inch intervals. The pen mark on the part was aligned with the graph paper grid to help me space the cuts. I would rotate the drill press table after each row was cut to the position of the next row. The rows were 1/4 inch apart. There were 16 plunges per square inch. The part was clamped down with two clamps during all cuts.

I am careful around machine tools and extra careful when I use them for purposes that they were not intended. The job took about half an evening. It turned out well.

Race bikes are taken apart and put together a lot, especially this one. The forks need to be taken off to remove the fairing. This means the triple clamp bolts will be loosened and tightened at least twice a year, if not more often. Past experience shows that repeatedly screwing and unscrewing steel bolts in aluminum parts will eventually create enough wear to cause a stripped thread. Murphy's law also applies. The stripped thread will occur when there is no time to fix it or the tools to do the job. Stainless threaded inserts were installed in all twelve of the triple clamp bolt holes to prevent stripping. I used Recoil inserts from Australia. They are sold by Fastenal and Ace Hardware. There are other brands that work, too.

Using hardened washers under the triple clamp bolts has been recommended to me. It seems to be a good idea. I could not find hardened stainless steel washers. Metric 8 mm hole diameter stainless steel washers are available and they are nice and thick. These washers are too wide to fit in the 0.5 inch diameter counterbores for the Allen bolts. They were ground on a grinding wheel to reduce the outer diameter using the little tool shown in the photos.

The inserts, washers, and some anti-sieze on the bolts will make these connections corrosion resistant, strong, and trouble-free.

Sooner or later a project gets done. The clamps are finished for now. This winter the bottom clamp will be milled to lighten it and both will be polished and painted black.

The only machine work was line boring the three clamp holes. All else was done by hand, a drill press, a Sawzall, or a bench grinder. We had to do it this way for budget reasons. If Santa Claus brought a Bridgeport mill this Christmas he would not be turned away. Machine tools are great things. Believe me!

The "W" shaped thing on the top of the bottom clamp is a steering stop. It contacts a tab on the frame and it prevents the forks from turning far enough to dent the tank. Four Allen bolts hold the stop to the clamp. Force applied to the stop will try to shear the bolts. It is good practice to reinforce bolted connections with pins when they need to resist shear. Hardened split pins are good for this application. Long split pins are shown in the picture. They cannot be cut with a saw so I trim two of them to 3/4 inches length with a cutoff wheel on an air grinder. Then I champfer the cut ends to match the manufactured ends.

Next I drill two 1/4-inch diameter holes in the stop plate 5/16 inch deep. These holes are at the areas that I want to reinforce with the split pins. I put two 1/4 inch diameter cabinetmaker's doweling pins in the holes. These are available at almost all shops selling hardwoods and woodworking tools.

Now, I lightly tighten the stop to the clamp with the four bolts. A good whack with a mallet, and the doweling pins dimple the clamp. I take the stop off and I take out the doweling pins. Holes 1/4 inch diameter and 1/2 inch deep are drilled in the clamp at the dimples. The split pins are tapped into the holes. A picture shows the doweling pin dimple and a hole with a split pin. The last step is to bolt the stop onto the clamp with the two split pins in place.

The doweling pin method works in aluminum. Steel dulls the doweling pins and they do not leave a mark.

This build diary shows basic shop work. Common screwups are mentioned, too. Things do not work right all of the time.

The Recoil thread inserts did not work well. The bolts would not easily screw into five of the nine inserts. I had to carefully run a tap through the installed inserts to clean up the threads. Then the bolts could be screwed in. The ninth insert was a problem. The tap got tangled up in the insert when I tried to remove it. The tap broke deep inside the threaded hole.

The proper tap removal method would be to take the forks apart and bring the triple clamp to a specialist with an electric zapper. They would blast the tap into smoke and ions with a strong electric current. Ever mindfull of our team's lack of money and time, I opted for another procedure. The Hillbilly method. Hee Haw! Tools for this travesty are drift punches, a big hammer, a magnet, needlenose pliers, and an ice pick or screwdriver. This is brutal. I put on my safety glasses.

Taps are made from high carbon or alloy steel. They are brittle. I put a drift punch in the hole and gave the broken tap a number of good whacks. I stuck the magnet into the hole and pulled out some shattered tap fragments, I pried loose a few coil threads with the ice pick, and I pulled them out with pliers. A flashlight helped. I repeated the pound, pick, pull process for seven or eight more times, then voila! The hole was clean. A new thread insert is needed. This is a project for another day.

It is important to align the forks correctly during assembly. Misaligned forks can cause a rough ride and all sorts of strange handling problems. This is one of many methods.

First, I make sure the steering stem bearings are in good condition and not loose, the fork tubes are not bent, and there are no cracks in the frame near the steering head. Then, I remove the springs and drain the fork oil and I insert the tubes into the clamps.

The triple clamp billets have true faces as described earlier. Portions of the true faces have been preserved throughout fabrication process. They are crosshatched with marking pen in the attached photo. The machining dimensions for the fork tube and steering stem holes were measured from these true faces. The distances between the true faces and the fork tube centerlines are the same, plus or minus a couple of thousanths of an inch. The true faces will be used to align the triple clamps.

I put a piece of flat glass against the clamps and I twist the clamps until all of both true faces touch the glass. How do I know the glass is flat? Flat glass will not rock if placed against the clamps when turned sideways or upside down. Warped glass will not rock if placed against the clamps one way and it will rock if it is put up against the clamps another way. I tighten the triple clamp bolts to keep them in alignment.

Now, I put on the front wheel and tighten the front wheel axle nut to the correct torque setting. I leave the clamp bolt loose on the bottom of the other fork tube. I raise the front wheel to almost full compression and set it on a crate. I grab the loose fork tube and wiggle it back and forth to center it on the front axle. Then I torque down the Allen bolt and both tubes are now clamped to the axle.

Next I measure the gap between the inside of the fork tube and the wheel spacer and I write it down in my notebook. I will space the fork tube this distance from the wheel spacer in the future when I change tires, etc.

Now I check to make sure that my front fender and fork brace do not spread the forks apart or pull them together. Occasionally shims or grinding are needed to make them fit. The last step is to refit the springs and to fill the forks with oil.

Nessecity "I am sure i have spelt that wrong" is the mother of invention nicely done. Broken taps are a real pain i have used the same method and its usually on the last hole you were going to tap,worse still if its a blind hole.

Logged

Newcastle born and bred a City built on Coal and Steel and a people built of stronger stuff

Yes, it was the last hole where everything went bad. The longer swingarm was put on this weekend with the longer chain, chaingaurd, brake hose, shocks and fender. This afternoon I took it out on our local mountain route for a good thrash after work. I was expecting it to be slow handling but stable, sort of like the Titanic. I was wrong. Instead, it was very stable with light precise handling and good roadholding. Very fast because I did not need to slow down much for corners. Tomorrow I will take it to Portland and back on the interstate for a final high speed test. Then, an engine tune and service, and the street hardware will come off and the tin will go on.

The chassis changes this year are based on advice from experts who race these things, posts on this forum, and my desire to try new ideas. In the past I increased rake to get more trail and stability. On this build I did not change the rake. Instead I made some triple clamps to decrease the offset. This increased the trail. The final result was a bike that was stable and handled well. It did not have the heavy steering associated with lots of rake. The swingarm was lengthened three inches and the overall percentage of trail to wheelbase is 8 percent.

This is my first experience with radial tires. They grip really good and they work best with a fluid and smooth cornering style. Lateral chassis stability is very important with these tires. The Triumph frame and modified swingarm are plenty strong but the forks were flexy. Making the forks stiffer using the new clamps helped a lot. It took that change to bring out the best in the radial tires.

The new triple clamps should grip the fork tubes as tightly as the original Triumph items. Triumph use galvanized 10 millimeter diameter by 1.25 millimeter pitch Allen bolts with a 27 Newton-meter dry tightening torque. What is the gripping force, I wonder?

I download a tightening torque chart from www.rpmmech.com/docs/tightening_torque.pdf These charts are not uncommon in the mechanical engineering world. The metric unit chart for M10x1.25 bolts lists the clamp loads for various strength bolts. I plot them up as shown on the attached chart. A 13.5 kiloNewton (3030 pound) load corresponds to a 27 Newton-meter tightening torque.

It is during the 4th July weekend when I do this and in a patriotic moment I decide to use American size bolts in the new clamps. Three eighths inch diameter bolts with Unified National Fine (UNF) threads are similar to the metric size. I am not thinking clearly and I drill and tap the holes for 5/16 inch diameter bolts with Unified National Coarse (UNC) threads. A smaller size. Then I helicoil the threads. This makes it almost impossible to make the holes bigger for the 3/8 inch bolts. What do I do?

I download the tightening chart from RPM Mechanical for 5/16 UNC bolts and plot up the clamp loads for various torques as shown on the attachment. A 15.5 foot-pound tightening torque corresponds to a 3030 pound clamp load. These charts are for typical galvanized bolts with clean, dry, and rolled threads in good condition. I will use anti-seize, a lubricant. A rule-of thumb is to reduce the bolt torque when the threads are lubed. I use a typical reduction value of 75%. The tightening torque will be .75 x 15.5 = 11.6 foot-pounds. I will use 12 foot-pounds. It is easier to remember.

Tensile stresses in the bolts produces the clamp loads and the clamp loads make the gripping power. A Grade 2 5/16 NC bolt produces a 2162 pound clamp force, maximum, using the RPM Mechanical chart. It is too weak. A Grade 5 bolt produces 3341 pounds clamping force, maximum. This exceeds the 3030 pound clamp load that I need, so Grade 5 bolts will be used.

The helicoils are stainless steel and I like to use stainless bolts. Thread galling can be a problem with stainless steel bolts tightened greater than Grade 3 limits, based on my experience. The situation is worse when the threaded parts are similar stainless alloys, and the bolts and helicoils are. The anti-sieze will prevent this problem but I might forget to use it. I will use galvanized Grade 5 carbon steel bolts. This should work OK with no seizing, I hope.

The attachments are too big. I will shrink them and include them in the next reply.

Ultimate tensile strength and clamping force are one thing but consider the fatigue strength of a bolt operating at close to its ultimate limit-- I'd use a grade 8 bolt instead of a grade 5; the difference in cost is small but the additional safety is worth a lot.

The crush and removal method for a broken tap was presented in a recent build diary entry. This procedure can be used for other purposes.

The Triumph steering head bearings were replaced several months ago. The bottom bearing outer race was easily removed using a slide hammer bearing puller. The top outer race was a different matter. The flange that supported the race had the same inner diameter as the race. The bearing puller could not hook under the race. What was Triumph thing about when they designed this?

Several removal methods were tried and none worked. As a last resort, a section of the race was ground 'paper thin" with the air grinder. Care was used to assure that none of the surrounding housing was disturbed. The thin part of the race was whacked with a center punch. The hardened race steel was brittle and it shattered. The bearing race was easily pried out.

Does the weld method work with arc, gas, or either? It sure seems to be a quicker procedure than the one I used. Especially for larger bearing races.

A few entries ago I mentioned how I damaged a helical coil insert and how I broke a tap inside of the coil when I tried to clean up the threads. I was cleaning the threads because the triple clamp bolts were binding in the coil inserts. I did some asking around and research. This is what I learned.

Helical coil inserts, like everything else, have their good and bad aspects. They are very sensitive to the quality of the leading edge of the first screw thread that contacts the coil. In general, there are few problems with manufactured bolts having undamaged rolled threads. Being a cheapskate, I did not buy new bolts of the correct length for this project. Instead, I used a sawzall to shorten a bunch of rolled thread bolts that were left over from an earlier project. Then tried to grind and trim the bolt ends to the correct shape. It was hard to do and it was especially difficult with the stainless steel bolts I used. The leading edges of the bolt threads were far from perfect. I bought some Grade 8 bolts with rolled threads in the correct length and it was readily apparent. The untrimmed bolts did not bind in the coil inserts, unlike my trimmed bolts.

Fixing the stripped threads where I removed the tap and helicoil was a problem. Most of the 5/16 x 18 threaded inserts I found had external threads with 1/2 inch or 7/16 outside diameters. Drilling and tapping for these inserts would make the bolt hole too large where the bottom of the Allen head screw contacts the clamp. Eventually I found some narrow inserts called Time Serts. I ground the shoulder off of the upper end of the Time-Sert. The ground shoulder had the same diameter as the outside diameter of the Time-Sert threads. Then I drilled the unthreaded portion of the triple clamp hole under the bolt head to 25/64 inches diameter. The Time-Sert would fit through this hole, barely. Next, I drilled and tapped the threaded portion of the hole with the Time-Sert drill and tap. Now I installed the insert.

The Time-Sert works OK. I was able to tighten the Allen bolt to the correct torque and the fork tube is firmly clamped in place. In hindsight, I would have used Time-Serts in all of the holes, initially, instead of helical coil inserts.

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